The present invention relates to a thin film spin probe used on spin polarized scanning tunneling microscopes. More particularly, the present invention relates to a thin film spin probe that is capable of measuring the spin-polarized components parallel with and vertical to the surface of a specimen.
A probe manufactured by cleaving semiconductor single crystals is used in an attempt to measure the spin-polarized components on specimen surfaces under a scanning tunneling microscope.
An example of measuring the spin polarized components using said probe is described referring to FIG. 6. In FIG. 6, 101 is a probe manufactured by cleaving a semiconductor single crystal. 102 is a specimen for measuring spin-polarized components. The specimen 102 comprises a magnetic film 102b (specimen) which is sufficiently thin to allow the transmission of excitation light and a transparent board or a substrate 102a (glass, mica, etc.) supporting said magnetic film. To measure, excitation light is transmitted through and vertical to the specimen as shown in the figure. The transmitted light is irradiated on the probe 101 to detect spin polarization perpendicular to the surface of the specimen 102b. 
The problems encountered with this method are:
a) To optically excite the probe, excitation light must pass through the specimen from the thin specimen side. This limits the thickness of the specimen.
b) Because the probe that is manufactured by cleaving semiconductors is thick, even when light is irradiated from the probe side perpendicular to the surface of the specimen, the excitation light can penetrate only 1 xcexcm into the surface at best, due to the large absorption constant. Efficient electron excitation at the tip cannot be expected.
c) Excitation light is incident from the probe side when measuring the components on the surface of a specimen (parallel components). Effective excitation is thus impossible because of the three-dimensional spread of the probe.
d) It is difficult to embed into a thin film spin probe a quantum structure designed to control spin polarization of excited electrons to enhance light emitting efficiency. It is therefore difficult to manufacture light emitting thin film spin probes.
With a view to solving these conventional problems, an object of the present invention is to provide a novel thin film spin probe by forming a thin GaAs/AlGaAs film on a GaAs board or a substrate using a thin film forming unit and by partly removing said substrate by selective etching.
The present invention further intends to solve the above problems by offering light emitting thin film spin probes comprising a GaAs substrate, a transparent support film made of AlGaAs, etc., formed on said substrate using a thin film forming unit, a thin film accommodating a light emitting region formed on said support film, and a thin barrier layer formed on said light emitting film, wherein said substrate is partly removed by selective etching.
The thin film spin probe of the present invention can be sufficiently thin as to allow excitation light to pass through it so that excitation light can be irradiated from the prober side, eliminating the restriction on the thickness of specimens to be measured.
It is also possible to alleviate the magnetic circular two-color effects that occur when the specimen excitation light is transmitted.
It is possible, by using semiconductor hetero-junction manufacturing technology, to embed a structure to effectively contain excitation carriers or a structure to control spin polarization.
Thin film spin probes are generally effective also for measuring the spin-polarized components that are horizontal with the surface of a specimen. In such an application, the thin film spin probes with a semiconductor hetero-junction can effectively contain carriers and alleviate the reduction in polarization that is one of the problems with single crystal cleaved probes.
As for light emission that is difficult to detect with a single crystal cleaved probe, the use of the quantum well structure enhances the efficiency of light emission. It is thus possible to measure spin polarization with a high sensitivity.